Convergent-divergent rectangular section nozzle

ABSTRACT

The disclosure of this invention pertains to a convergentdivergent rectangular section nozzle for jet propulsion engines. To convert the nozzle into a convergent-only configuration one of the four walls of the divergent part is movable into a position adjacent the convergent part thereby allowing the ambient slipstream to enter the nozzle immediately downstream of the throat thereof.

United States Patent Inventors Ralpb Mureb Denning;

Reginald l-larold Wlltsbire; Stephen Sales; Alexander Scott, all of Filton, Bristol,

CONVERGENT-DIVERGENT RECTANGULAR SECTION NOZZLE 4 Claims, 5 Drawing Figs.

11.8. CI. 239/456, 60/230, 239065.31, 239/265.33 lat. v 1105b 1/32 Field of Search ..239/265.19, 265.31, 265.33, 456, 455, 505, 506, 507, 509, 510; 60/228, 230, 231

an n

I l g I I3 02 Primary Examiner-M. Henson Wood, Jr. Assistant Examiner-Thomas C. Culp, Jr. Attorney-Mawhinnejy & Mawhinney ABSTRACT: The disclosure of this invention pertains to a convergent-divergent rectangular section noule for jet propulsion engines. To convert the nozzle into a convergentonly configuration one of the four walls of the divergent part is movable into a position adjacent the convergent part thereby allowing the ambient slipstream to enter the nozzle immediately downstream of the throat thereof.

PATENIED AUG 3 ISYI 3, 596; 836

sum 2 BF 4 RA Muncu DEI/AV/N PTA/- HY MM AT KS.

PATENIED AUG alsn 3,596,836

sum u 0F 4 SO 45 42 8O 44 45 5O 86 B) 1% /MMW CONVERGENT-DIVERGENT nncunciurjtn 'sncnou NOZZLE This invention relates to a jet nozzle for'jet pro pulsior rengmes.

It is known for such noules to have a c nvergent' upstream part and a divergent downstream part. It also known in axisymmetric noules forthe convergent-divergent shape to be defined by a bulbous center body and forthe downstream part i to comprise an annular shroud which is movableinthe up stream direction into a position surrounding the upstreampart of the nozzle so that, when required, the .nozzlecan be con-- verted from a convergent-divergent shape into-a shape which is convergent-only. I

in operation, when the pressure ratio of the nozzle is sufiiciently high to obtain a performance improvementfrom convergent-divergent configuration the shroud is rnoved into the downstream position. lfthe nonle pressure ratio not sufficient for the gases to expand against the cont'mesof the divergent part, the shroud is retracted so as to admitthe 'ambient slipstream to the downstream part'and thereby avoid aerodynamic drag at the base of the "shroud,

Such nozzles have the disadvantage that ni pm of the nozzle structure has to be supported as acantileverbecause the upstream part of the nozzlejcannotbe laterally-connected to supporting structure because, asstated, theupstream part: is surrounded by the shroud when'the latteris It is also known for convergent-divergent nou'les .to' be of rectangular cross section but it hashitherto'not been proposed to provide the latter "with a retractable shroud. Such 'aurectan gular section shroud would have the additional 'difliculty' of being relatively heavy because the irectangtdarshapezdoes not have the natural hoopstrength ofa circular Ind-would '3 have'to be provided with stiffening structure.

I The present invention provides in a jet propulsion engine :a convergentdivergent nozzle -of .rec'tnngular cross' sectiou 'in which to above difficulties :arrovercome that the downstream part of the nozzle 'comprisesd'our .rectangularly 140 related walls one of which :is movable betweenafirstposition -in which it cooperates-with the remaining three "walls to .en-

close the downstream part and aisecond positionrin'which one wall is situated adjacent to lthefupstream 'part:so:that one side of the downstream part is =open Iohhe ambient-at- FIG. 3i; apartly'broken away xplanviewofflc; {Zsectioned 0 1 on the line Ill-Ill in FIGA.

FlG.-4'is an-end-view of FIGJ. H6. 5 is-an enlarged detail'of FIQA.

Referring to the drawings,=the nozzlecompriaeeaaround sec tion "main duct 30leadingxto two i'ectangular. sectionrbranc'h -55 ducts 3L'An exhaust gas flow front-a'jetipropulsion engine :32

isexhaustedthrough the ducts31.

'Ea'ch duct 31 is defined by anouter wall 33 ,ari inner'wall 34 and:opposite sidewalls 35, and therductiterminatesfatzamozzle throat .36 of rectangular shape. The walls 35,"34'are=conver- :70

gent'and the walls 35am divergent-all in ordento v'charrgefrom the round to the rectangular sectiongbut'theactualicrossaectional area of the-ducts31isreducing' towards'iheithroatiflfi; i.e. the crosssection at the 'throat ofleachduct'fl-lislessihan half .the cross section of the idiict SOQiIhe-rreductionin-area anected-tothmpanelby a'fitting 63. lhe:pulleys6lat the upper mosphere, means being :provided formoving ione' wall maybe either by virtue of the'shaping of the walls 33; 34, 35 and/or by th'e'introduction of vanes 37 at the throat.

Each duct- 31 is secured at or near the throat 36 to two parallel walls 38 which extend both upstream and downstream ofthe throat as shown. The walls 38 aresecured together by a center body-39 and between themthe walls 38 constitute the main load-bearing structure of the nozzle. I Y

Downstream of the throat 36 the nozzle comprises a pair of ducts 40each principally defined by the parallel walls 38 and. a surface4l of the body 39. The surface 41 is understood to extend fromthe throat 36 to the downstream end of the body 39, the surface 34'extending between the throat and the upstream end of the body'39. ln'respect of each duct 40there is .provided a panel 42 supported on the walls 38 for sliding-motion between a position A in which the panel'42 faces the surface dland-a position 8 upstream of the position A and-such that the downstream edge 43, of the panel lies substantially at throat 36. When the panel is in the position A the duct 40 is enclosed atall four sides and-constitutes a divergent-continuation ofthe convergent duct 31, the divergence arising wholly from the divergence as shown between surface 41' and the panel 42. When thepanel 42 is retracted into position B the duct-Wis open laterally, e.g. for the purpose of allowing ambient air to enter the duct under circumstances referred to laterherein when the operation of the nozzle is described.

, For the purposeof supporting the panels for said sliding motion thereof, each panel is provided at theedges thereof ad- 'jacent the walls 38 with a recirculating roller bearing 45 cooperating with a track secured to the adjacent wall 38.1 Each panel 4ziis'made of relatively thin sheet material and is therefore flexible so that whenthe panel is in the position A gas pressure in-the duct 40tends to bow the-panel outwardly and causes it to be stressed intensionin a direction primarily transversely to the -lengthof the duct. The 'tracks are arranged for the bearing surfaces, 47, thereof to face away from the :rnedicalpartof the panel so astobe positioned to provide the reaction tosaid tension. ilo keep'the tension :within reasonable 'proportion'ihe -panel is formed into a preset circular 511,65 '-shown.in FlG. 4,'about=an axis parallel to-the-nozzle axis,'i.e. as if deformed by the gas pressure. 'Further,-the tracks are of circular arc'section, i.e. thesurfaces 47 are curved to a *radius48 about a center-49 (FIG. 5) so that the panel can pivotrelative to the walls 38 by a limited amount as may be requiredato accommodate changing patterns of stress between the'ipaneliandzthose walls. The'center of such pivotalmotion is essentially thecenter 49;

Undue flexing of the panels 42 is :prevented by ribs 44 secured to each panel at theoutside thereof so that if the panel tends-to fleXinwards'theribsM engageteach other to prevent such-flexing.

Theiconnection between each panel- 4'2-and'its associated bearings 45 is by-means of :brackets 50 secured to the panel antterttending-archedlyoverthe adjacenttracks46 so that the bearing-4S is in a position tangential-to the panel (FIG; 5). "More=specifically,'the rollers,5l, of the bearing rotate in a plane tangentialto thepanel. The-active and return runs of the" rollerszare denoted52 and-53,-respectively. A location 54iis :providedto-prevent thepanel beinginadvertentlymoved-from the tracksbyastray force acting to 'move the-panel-bodily,-i.e. :a'force whichis not converted-into tension across the panel. This is-necessarybecause' the curve of "the'tracks is not necessariilysufiicientto retainathe bearings onthe'tracks.

Therbracketsi50 and tracks46 includea seal formed-by a'lip .55-'on= the-bracket cooperating'with asurface 56 (also curved about the center-49) 'on 'thetrack-to inhibit pressure loss from 'theetiuctio' whenvthe panel M2 is .inposition "A. "At the up- :streamaendaofthe ;panel-42-the lips55 adjoinalip 57 (F1642) :rextendingacross'thepanel to seal the upstream end thereof .against a'flip 58onthe wall 33.

.Eachpanel 42iismoved'by cable drives comprisingadjacent each1rack 46 acablef60 trained-overpulleys'fil 62 supported and the lower panel are secured to shaft 64 and 65 respectively (FIG. 2). The shaft 64 is adapted to be rotated by an air motor 66 and is connected to the shaft 65 by a cable drive 67. Thus rotation of the motor causes both panels to be driven from the position A to the position B or vice versa.

The nozzle is secured to a support structure 70 (FIGS. 1 and 3,) by lugs 71. The structure 70 is in turn secured to an aircraft wing structure 73 by lugs 74 and members 75. The engine 32 is connected to the wing structure 73 by an engine mounting 76. The ducts 31 are, as mentioned, secured to the walls 38. The connection between the ducts 31 and the engine is by means of a joint 77 connected between the duct 30 and the exhaust pipe, 78, of the engine in such a way that the ducts 31 and the engine can move relative to each other in the direction of the length of the ducts to accommodate changing stress patterns.

The nozzle includes in respect of each panel a fairing 80 separating the part of the nozzle structure upstream of the throat 36 from the ambient air, i.e. from the slipstream which in flight passes over the upper surface, 81, of the wing and over the undersurface, 82, of a nacelle 83 enclosing the engine. Each fairing 80 terminates downstream at an edge 84 lying at the throat 36 adjacent the edge 43 of the panel 42 when the latter is in the position B. Further, each fairing 80 is extended over each of the adjacent walls by means of branch fairings 85 terminating at streamlined points 86.

In operation, when the pressure ratio across the throat of the nozzle is such that the pressure of the gas in the ducts 40 is significantly above ambient pressure, considerations of noule efficiency require a convergent-divergent nozzle. This is well understood per se. The requirement is satisfied by moving the panels 42 into the position A. The ducts 31, 40 then form a convergent-divergent nozzle and the expanding gases fill the ducts 40 and produce a jet J1. The propulsive thrust obtainable from the expansion of the gases in the ducts 40 acts on the surfaces 41 and is transmitted by the parallel walls 38' to the structure 70 and thus to the aircraft'When the pressure in the f ducts 40 is not significantly above ambient pressure the gases tend to adhere to the body 39 to produce a jet J2. in this condition the base area, 87, between the edges 43 of the panels 42 and the jet J2 can give rise to undesirable flow separation and consequent drag on the aircraft. To overcome this the panels are withdrawn into the position B whereby the slipstream over the surfaces 81, 82 can enter between the walls 38 to join the jet .12, substantially at the throat 36.

The branch fairings 85 are introduced partly to protect the tracks 46 and partly to provide rounded edges for the walls 38 to enable vortices being formed at these edges by the 'slipstream outside the walls 38 to discharge with minimum turbulence over the walls and downstream over the points 86.

divergent part of the nozzle. The panels 42 constitutea simple. means of laterally opening the divergent ducts and the seals- 55, 56 and 57, 58 provide the necessary sealing facility in a manner not substantially influenced by the inevitable thermal distortion of the nozzle. Also, the fact that only 'a part as distinct from the whole of the divergent part is retracted to provide the lateral opening, means that the nozzle construction can have powerful load-bearing attachment to the aircraft structure right to the downstream end of the nozzle structure.

What we claim is:

l. A jet nozzle for a jet propulsion engine comprising four rectangularly related walls one of which is translatable in the direction of the length of the nozzle relative to its two adjacent walls, the translatable wall extending curvedly awa interior of the nozzle between two edge portions 0 the trans latable wall parallel to the length of the nozzle, the translatable wall being made of flexible sheet material so as to accommodate thermal and like structural changes by changes in curvature, in respect of each of said edges and bearing means having a fixed part adapted to support the edge portion for the translation of the wall and further adapted to support the edge portion for pivotal movement about an axis parallel to the direction of translation to accommodate said curvature changes.

2. A jet nozzle according to claim 1 each fixed part having a bearing surface facing away from the translatable wall and the adjacent edge portion having a cooperating bearing surface facing towards the wall, whereby the tension created in the curved wall by the pressure of the gases in the nozzle is reacted by pressure between the bearing surfaces.

3. A nozzle according to claim 2, wherein one of the bearing surfaces is curved about an axis parallel to the length of the adjacent edge portion to accommodate said pivotal movement.

4. A nozzle according to claim 3, wherein a seal between the translatable wall and each of the walls adjacent thereto comprises a first and second seal elements provided respectively on the translatable wall and on the adjacent wall, and wherein at least one of the seal elements is curved about said axis of one of the bearing surfaces to accommodate said pivotal movement.

from the 

1. A jet nozzle for a jet propulsion engine comprising four rectangularly related walls one of which is translatable in the direction of the length of the nozzle relative to its two adjacent walls, the translatable wall extending curvedly away from the interior of the nozzle between two edge portions of the translatable wall parallel to the length of the nozzle, the translatable wall being made of flexible sheet material so as to accommodate thermal and like structural changes by changes in curvature, in respect of each of said edges and bearing means having a fixed part adapted to support the edge portion for the translation of the wall and further adapted to support the edge portion for pivotal movement about an axis parallel to the direction of translation to accommodate said curvature changes.
 2. A jet nozzle according to claim 1 each fixed part having a bearing surface facing away from the translatable wall and the adjacent edge portion having a cooperating bearing surface facing towards the wall, whereby the tension created in the curved wall by the pressure of the gases in the nozzle is reacted by pressure between the bearing surfaces.
 3. A nozzle according to claim 2, wherein one of the bearing surfaces is curved about an axis parallel to the length of the adjacent edge portion to accommodate said pivotal movement.
 4. A nozzle according to claim 3, wherein a seal between the translatable wall and each of the walls adjacent thereto comprises a first and second seal elements provided respectively on the translatable wall and on the adjacent wall, and wherein at least one of the seal elements is curved about said axis of one of the bearing surfaces to accommodate said pivotal movement. 